Measuring and testing – Vibration – By mechanical waves
Patent
1988-09-07
1990-01-02
Chapman, John
Measuring and testing
Vibration
By mechanical waves
73599, G01N 2904
Patent
active
048904961
ABSTRACT:
A method for detecting hydrogen attack by ultrasound wave velocity measurements in which ultrasound waves (e.g. longitudinal, shear, or creeping) are transmitted from one transducer to another transducer along a fixed path through a steel body such as pipe. The velocity of the ultrasound wave is determined with an accuracy of 0.1 percent from the fixed path length and the time for a wave to travel from one transducer to the other transducer. A decrease in velocity by more than two percent indicates hydrogen attack. In one embodiment, either refracted longitudinal or refracted shear waves are transmitted, and the velocities thereof are determined. In another embodiment, a creeping wave is transmitted from one transducer to the other transducer with the creeping wave including a surface wave and a subsurface wave. Travel time of the subsurface wave is measured and used with the known fixed path length in determining velocity. In the third embodiment ultrasonic waves are transmitted into the material and the backscattered ultrasound is measured. An increase in backscattered ultrasound is related to hydrogen attack.
REFERENCES:
patent: 3416365 (1968-12-01), Frederick
patent: 4386527 (1983-06-01), Maucher
patent: 4685334 (1987-08-01), Latimer
Szilard, J., "Ultrasonic Testing" pp. 612-621 (1982).
Singh, "Inspection for Hydrogen Damage in Boiler Water Wall Tubes" Materials Eval. (1985), Sep.
Watanabe et al, "Ultrasonic Velocity Ratio Method for Detecting and Evaluating Hydrogen Attack in Steels" ASTM, pp. 153-165, May 22-24 (1984).
Failures & Inspection of Fossil-Fired Boiler Tubes: 1983 Conference & Workshop, CS-3272, Contract WS 82-101, Dec. 1983, Articles: a. "Inspection for Hydrogen Damage in Waterwall Tubes Using Ultrasonic Techniques", Sloat et al., b. "Mitigating Forced Outages by Selective Replacement of Boiler Tubes" Loper et al., c. "Working Group on Hydrogen Damage, Pitting and Deposits", Freeh et al.
Alcazar David G.
Birring Anmol S.
Hanley John J.
Hendrix Gary J.
Chapman John
Electric Power Research Institute
Fess Lawrence
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